When the massive Women's Health Initiative study was abruptly halted in 2005, it was clear that estrogen-plus-progestin hormone therapy increased the risk of breast cancer in women. Now 11 years of follow-up on women in the study who took hormones shows that their risk remains higher and that they have an increased danger of dying from the disease.
The original study was based on data from women who had been taking hormones for an average of about 5 1/2 years. However, researchers at the Los Angeles Biomedical Research Institute continued to track more than 12,000 of the women enrolled in the study.
The researchers found 385 cases of invasive breast cancer ( cancer that has spread) in women who took estrogen-plus-progestin hormone therapy during the study, compared with 293 cases of breast cancer in women who took no hormones.
The increase was found for all types of breast cancers, not just the so-called estrogen-receptor positive breast cancer believed most likely to be spurred by hormones.
Moreover, those who took hormones and then developed breast cancer were more likely to have positive lymph nodes — an indication that the cancer has spread. Almost 24% of the women who took hormones and were diagnosed with breast cancer had positive lymph nodes compared with about 16% for breast cancer patients who had not taken hormones.
The study, published Tuesday in the Journal of the American Medical Assn., found 25 deaths from breast cancer in the hormone therapy group compared with 12 breast cancer deaths in the placebo group, which would translate to one more death per year per 10,000 women.
"We've shown that all categories of breast cancers were increased and there were increased deaths in breast cancer," said Dr. Rowan T. Chlebowski, the lead author of the study and a medical oncologist with the Los Angeles Biomedical Research Institute.
Participants in the Women's Health Initiative, however, took hormones at higher doses than are typically used today, critics have pointed out. The study also focused on older postmenopausal women, and questions linger today about whether hormone therapy might benefit younger women without increasing risk.
Doctors now recommend hormone therapy only for women with severe hot flashes or other menopausal symptoms and only for a year or two. But research is needed on whether even one or two years of hormone therapy increases the risk of breast cancer, Dr. Peter B. Bach of Memorial Sloan-Kettering Cancer Center in New York said in an editorial accompanying the study.
The longer these women are followed, the more dangerous hormone replacement therapy is going to look, Bach wrote.